Plaster lath



March 19, 1929. owsm 1,705,775-

PLASTER'LATH Filed 001:. 27, 1924 INVENTOR cfohn F. Makowslci,

BY Q sum ATT RN EY teases ties as, ma

course srarss ilQEfill", MBKO'WSKI, OF STOGKTO N, CALIFORNIA, .ASSIGNORT0 PRODUCTS COMPAINY, or STOCKTON, CALIFORNIA, A GOR'PQEAEEXQET.

PLASTER LATE.

I Application .filed fictobci' 27, 1824. Serial Ito. 746,956.

" that type wherein finely divided -mineral fragments are adhered to thesurface of a base consisting of wall board of that type wherein a coreof plastic material is adhered between two surface sheets of heavy paperor the like. a The mineral fragments form the key for the plaster whichis spread over the lath. One of the essentials to a successful lath ofthe type under discussion is that the paper surface sheets be ver firmlyadhered to the core of the base boar Otherwise the weight of the gravelplus the plaster spread thereover would peel or tear such surface sheetfrom; place and render the lath a failure.

The object of my invention therefore is to construct a lath of the typedescribed in which an adhesive element is introduced into the core ofthe base board, which adhesive is of a special nature to mix with theplasticcore in such a mannras to cause a practically inseparable bondbetween the core and surface sheets.

The figure of the drawing is a cross sectional view of a piece ofplaster lath of the type under discussion.

. Referring to the numerals on the drawings,

1 and 2 designate the surface sheets of thick paper or the like ,whilethe numeral 3'designates the interior core of the wall board to whichthe sheets are adhered.

In the past and before I commenced to use plaster board of thischaracter as a base for plaster lath it was common ract-ice to make thecore of the wall board 0 gypsum plaster with saw dust or the like as afiller, the plaster predominating by volume. llhe adhesiveness of theplaster was relied upon to adhere the surface sheets to the core. r

Experimentation however proved to me that the adhesion of the paper tothe core under the above method of making the board was insufiicient toprevent the aper from peeling oh? the corewhen the a ded weight of themineral fragments, shown at 4 on the drawing, plus the plaster 5, wasspread over till the surface sheet. This was true even when a largevolume of plaster anda minimum amount of saw dust was used.- Acommercial lath however must'be inexpensive and light and therefore inmaking the lath I same time add elements therein in suspension as a@Qfi'lyiymlau use about an equal amount, by volume of the saw dust orlike filler, and plaster.

With these proportions when the material is mixed with water into amoist semiliquid form for introduction between the surface sheets themass lacks viscosity to such ere tent that the gypsum (the adhesive) inthe mass precipitates to the bottom Thus as the core hardens and setsthe greater portion of the adhesive element will be adjacent sur facesheet only. Consequently the other sheet will not properly adhere to theas any one of the surfaces may be-the which the mineral fragments i andI 5 may be adhered it is unsafe to use such last described board as abase for the lath, as the whole plaster key and plaster might peel off,particularly on ceiling work.

It is essential therefore that an element be introduced into the masswhich will sustain all the ingredients therein in suspension while thesame is hardening and setting After careful experimentation found thatthe properties of dentrin are such as to serve the purpose desired, andat the greater adhesive qualities to the mass.

By thoroughly mixing the plaster, sawdust,

water and dext'rin together, the'properties of the d'extrm cause themassto be viscous or glutinous to such an extent as to hold whole andpositively prevent precipitation of the lime to the bottom. At the sametime dentrin itself is an adhesive, so when the permea= tion of thesurface papers is had there is a complete, uniform adherence between themass and both surface sheets.

I have further found by experiment have that by reason of the VISCOSItyof mass when mixed with the dextrin a much l dust to remain uniformlydistributed throughout the mass, whereas when plaster alone is used andthe precipitation takes place the saw-dust tends to float more to thetop, which action also hinders the production of a perfect base board.

In addition to the above, the properties of dextrin are such that, whenmixed with the gypsum in the plaster it forms an insoluble adhesive.This insolubility causes the mass to adhere closely to the paperscommonly used for the surface sheets of the wall board. Furthermore thedextrin adhesive as thus used will not soften under heat and for thisand the above reasons will firmly hold the mass and the, covering sheetstogether and will totally eliminate the troublesome peelers.

This then permits the plaster lath to be built up on a base board of thetype described, which'lath will have an all key surface and be capableof holding the plaster or other applied finish in a most effectivemanner. Also such a lath can be manufactured at a cost to allow it tomeet commercial price competition.

Having thus described my invention, what I claim as new and useful anddesire to'secure by Letters Patent is:

A plaster lath including a supporting member comprising plaster boardhaving a center core containing dextrin as an'adhesive to ad here thecore to the surface sheets, and a plaster key of comminuted mineralfragments adhered to the outer face of one sheet.

In testimony whereof I aflix my signature.

JOHN F. MAKOWSKI.

